Electrical cables and wire rope often comprise a plurality of individual strands which may be stranded together by mechanisms such as those disclosed in U.S. Pat. Nos. 3,827,225 and 3,902,307. During wire stranding operations, one or more individual wire strands are helically wrapped over a core wire to form a multi-strand cable. The individual strands usually consist of bare wire and it has become common practice in the art to apply some type of protective coating compound onto the cable in order to protect the cable from deterioration. It has been found that without the presence of such a protective coating, moisture and other contaminants accumulate in the numerous interstices existing between the wire strands and such contributes to and accelerates the corrosion of the cable thereby shortening its useful life.
A multistrand cable such as that shown in U.S. Pat. No. 3,647,939 used for transmission of electrical power often has at least one high strength strand to reinforce the cable. Such reinforcement is particularly desirable in overhead conductor applications because of tensional stresses associated therewith. While the reinforcement strand may be an aluminum alloy as disclosed by U.S. Pat. No. 3,647,939, other metals such as ferrous metals are often used. One example is the conventional ACSR (Aluminum Conductor Steel Reinforced) type cable.
Since overhead conductors are routinely exposed to the elements, such as rain, salty coastal atmosphere and other corrosive environments, and since the reinforcement strand may also interact corrosively with the other strands, cable manufacturers normally take special steps to minimize deterioration of the reinforcement strand. Such steps include galvanization of the reinforcement strand and application of a corrosion inhibitor coating to the strand. One method of applying coating to the strand is to submerge an entire roll of strand in grease or some other coating prior to mounting in the strander mechanism. However this method is inefficient, and messy because the coating is not uniformly applied to the strand and such method promotes unpredictable dripping and dispersion of coating material onto other strands, the strander mechanism, and adjacent apparatus.
Another method used in the art is to spray the coating compound onto the strands at a location just upstream of the closing blocks of the strander so that the multistrand cable is coated with compound when it exits from the closing blocks. This technique is disadvantageous in that the compound is not uniformly distributed over the wire strands with the undesirable result that as the cable exits from the closing blocks, it has some portion which are lumped with an excessive amount of compound, other portions which are covered with a very sparse amount of compound, and portions which are not covered at all. Since the compound is applied to the strands by spraying, much of the compound avoids contacting the strands altogether and therefore a recovery system must be used to collect the unused compound and recirculate it back to the spray nozzle. Furthermore, due to the uneven and inconsistent application of the compound, the resultant cable has a poor quality which detrimentally affects its commercial value as well as its possible fields of use.
Other methods include passing all strands through a fluid bath as shown by U.S. Pat. Nos. 3,885,380 and 3,889,455. However these methods also require elaborate compound recovery systems, limitations on stranding speed and productivity, and additional steps such as rewinding.
The state of the prior art is taught by U.S. Pat. No. 3,923,003 wherein flooded multistrand cable is produced by applying a coating of flooding compound onto a bare wire strand and then using the coated strand as a center strand in a stranding operation. The bare wire strand is coated with compound by passing it through a bath of viscous flooding compound and as the coated strand exits from the bath, it is drawn through a restricted opening in a rubber wiper disc. The wiper disc removes excess compound from the coated strand and forms the remainder thereof which adheres to the strand in a uniform coating. The coated strand is then used as the center strand in a stranding operation during which a plurality of bare wire strands are tightly wrapped in a helical fashion about the periphery of the coated center strand to thereby form the multistrand cable. A set of post formers then compress and squeeze the multistrand cable into a symmetrically round cable product and the compressive action is sufficient to extrude and force the compound from the coated center strand outwardly through the interstices existing between the wrapped peripheral strands. The compressive action of the post formers effectively distributes and spreads the flooding compound over the entire surface of each strand to thereby produce a flooded multistrand cable having a round cross section and a uniform coating of flooding compound along its whole length. While this method of coating the wire is very efficient, it normally requires one step for coating the core wire and then a second step for stranding the cable. The steps may be performed in line to produce a continuous coating and stranding process, but since the coated core wire must then travel through the length of the strander, a coating such as grease may become contaminated, lose uniformly, drip from the core wire, and be removed from the core wire by contact with various portions of the strander.
The present invention solves the prior art problems while reducing the process to a single efficient step.